Google, Apple, Yahoo, Facebook: Who gives the government the most data?

Today, following in the example of a lot of the tech companies at the center of the National Security Agency data-gathering scandal, Yahoo released the number of requests it had received for private user data from the government, according to the Silicon Valley Business Journal.

None of the companies can say exactly what kind of data is being requested, or for what reason. They all give totals that lump a number of different things in together -- from emails obtained by the NSA through secretive national security letters to relatively mundane data like billing addresses given to law enforcement and the courts to comply with warrants and subpoenas.